The Milky Way Could Potentially Host a Hundred Times More Habitable Planets

The number of planets with potential conditions for life formation in our galaxy could be significantly higher than previously thought. According to information presented by Rutgers University's planetologist Lujendra Ojha at the Goldschmidt conference in Lyon, France, this figure may reach a hundredfold increase, as reported by Vice.

Scientists have discovered that subsurface water bodies on planets orbiting red dwarf stars, which are significantly smaller than our Sun and the most common type of stars in the universe, can also be potential habitats for life. While life on Earth originated in the oceans, researchers have now found that similar conditions may exist in subsurface oceans on planets orbiting red dwarfs. This discovery plays a crucial role in the search for extraterrestrial life, as red dwarfs often host rocky planets similar to Earth in their systems.

Lujendra Ojha presented evidence of geothermal heat within many "exo-Earths" – Earth-like planets in other stellar systems. A study published in Nature in late 2022 showed that these subsurface oceans in red dwarf systems could provide favorable conditions for life over extended periods. Ojha and his team modeled exoplanets based on real examples and studied the dynamics of subsurface ocean melting. The results indicate that even small flows of geothermal heat can melt subsurface water reservoirs beneath frozen layers on distant exoplanets. This suggests that these hidden oceans are likely abundant in red dwarf systems throughout the galaxy.

Currently, scientists believe that the challenge of life emergence on planets orbiting red dwarfs lies in the close proximity of the habitable zone to the star. Planets located too close to the star become tidally locked, with one side always facing it. This phenomenon, known as orbital resonance (e.g., the Moon always facing Earth on one side), creates a stark temperature difference between the planet's two hemispheres (day and night), with scorching heat on the subsolar side and temperatures approaching absolute zero on the dark side. Consequently, strong winds can occur in the planet's atmosphere.

Red dwarfs are also much more active than the Sun, with powerful flares that can be detrimental to surface life. However, these flares can be mitigated by strong magnetic fields, which such planets typically lack. Therefore, subterranean oceans remain one of the few viable options for the origin and development of life.

Although Earth is the only planet with oceans in our solar system, some of our system's satellites, such as Jupiter's moon Europa, may also have subsurface oceans. Europa is considered one of the most likely places for extraterrestrial life in the solar system.